A buffer overflow was addressed with improved bounds checking. This issue is fixed in macOS Catalina 10.15, tvOS 13, iTunes for Windows 12.10.1, iCloud for Windows 10.7, iCloud for Windows 7.14. Processing a maliciously crafted text file may lead to arbitrary code execution.
https://support.apple.com/kb/HT210722
https://support.apple.com/HT210637
https://support.apple.com/HT210636